How Wood Stoves Achieve a Clean Burn

The Environmental Protection Agency closely monitors how wood stoves burn fuel. When purchasing a wood-burning stove, you always want to look for models that carry an EPA certification, which confirms that the stove meets efficiency standards that are good for our environment. The EPA’s goal is to certify stoves that provide the most effective burn possible.

What is “primary air”?

Air is necessary for a fire to happen. Without air – and heat and a fuel source – there can be no fire. Primary air is the air that the user of a wood stove controls with a valve or dial or some other method to bring air into the burn area.

Prior to the EPA’s certifying of wood-burning appliances, methods for introducing air into the firebox didn’t do a very good job distributing the air, resulting in incomplete burns, particularly when burning at low levels. And the result of this was unburned, combustible gasses given off by the wood going up the chimney and into the environment.

A better air-delivery method

In most modern EPA-certified stoves, the primary air flows into the firebox through a slit that runs across the top of the box. This makes for an even distribution of air and results in more efficient burns.

Furthering this process is a secondary combustion air flow that prevents unburned gasses from entering the flue. Secondary air is brought to the system through a catalytic combustor or a non-catalytic combustion system.

Catalytic combustors

In order to receive certification from the EPA, stoves must employ a way to create efficient burns. Stoves with catalytic combustors channel excess smoke into a device (combustor), where it is burned and turned into heat rather than pollution. The dual benefit is more heat for you, and fewer toxins for the environment.

The catalytic convertor is made of ceramic in various shapes, depending on the stove model it will be put into. A number of channels run within the device. At specific temperatures, the coating on the converter reacts to lower the smoke’s ignition temperature, causing it to burn.

Non-Catalytic stoves

Stoves don’t have to use catalytic technology to receive EPA certification. Appliances can be certified as long as they prove efficient. Non-catalytic stoves accomplish essentially the same thing as the catalytic models, only they do it through a secondary air system. These stoves cause gas and smoke to ignite by injecting air into the firebox in just the right quantity and locations.

This is done with tubes made of stainless steel that contain perforations and are installed across the top of the firebox. The result is more air than is available with just a primary air source, causing a much more complete burn of the fuel load and smoke. The air sent into the firebox with a non-catalytic system is controlled entirely by the appliance.

What’s your best choice?

Catalytic stoves tend to be more efficient and provide longer burns than non-catalytic stoves. They do very well with low burn cycles. Non-catalytic stoves normally create more vibrant-looking fires and are a little easier to operate. In making your choice, talk with a hearth and stove expert and determine the best type of stove for your specific needs.

Marsh’s Stoves & Fireplaces of Toronto has a variety of handsome and efficient wood stoves employing both the technologies we talked about here. Stop by our showroom at 3322 Dundas Street West and get the right answers and advice. You can reach us by phone at (416) 762-4582.

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